The Third Wheel is a level in the video game World of Goo. It is the sixth level Chapter 3. In this level the player is introduced to Spike Goo. Players must use the sticking ability of Spike Goo to transport the structure with Small Beauty Goo to the exit by attaching Spike Goo onto the rotating wheel-like creatures. The titular third wheel is spiky and only 4 small knobs are safe for Spike Goo to be attached to. Skull Goos, making their final appearance, have to be used to prevent the structure from being destroyed before reaching the gears located on top of the cliff. Gears break up the structure without destroying any Goos so that they fall down the shaft to where they can easily be lead to the pipe.